1. Field of the Invention
The present invention relates to a device for operating a roll-screen and, more particularly, a device for raising, lowering and stopping a screen cloth of a roll-screen.
2. Description of the Prior Art
The conventional roll-screen includes a screen cloth, a winding roll for winding up the screen cloth, a coil spring connected to the winding roll to continually applying resilient force to rotate it in its cloth winding-up direction and a ratchet device which utilizes centrifugal action acting thereon to stop said screen cloth at a desired lowered position. When it is desired to raise the screen cloth, said cloth is slightly pulled downwardly to release said ratchet device from the winding roll, thereby allowing the screen cloth to be wound up onto the winding roll under the action of said coil spring.
According to the mechanism for raising, lowering and stopping the screen cloth of the conventional roll-screen, it is very difficult to stop the screen cloth at a desired height.